1. Field of the Invention
The present invention relates to an image forming apparatus, a method for controlling the same, and a storage medium.
2. Description of the Related Art
Many of conventional multifunction peripherals (hereinafter referred to as MFPs) have a function of entering a power-saving state providing lower power consumption, for example, by stopping supplying the power to some circuits or stopping supplying a clock, when a standby state continues for a certain period of time, thus reducing power consumption. The above-described power-saving state providing low power consumption is sometimes referred to also as a sleep state (power-saving mode).
It is desired that, when an MFP in the power-saving state detects a signal input from a device connected to an external interface, the MFP returns to an operating state from the power-saving state, and then executes a predetermined job from a user. Specifically, the external interface refers to a facsimile (FAX) controller and a local area network (LAN) controller, and the predetermined job refers to a FAX reception job and a print job.
The MFP returns to the operating state using as a trigger a calling indicator (CI) detection signal input to the FAX controller via a telephone line. Then, upon reception of data following the CI detection signal, the MFP becomes able to receive a job during the power-saving state.
Even in the power-saving state, the MFP supplies the power to the LAN controller provided outside a main central processing unit (CPU). Upon reception of a packet from outside via the LAN controller, the MFP returns to the operating state and responds to a print request from a personal computer (PC).
During a copy operation, the user directly returns the MFP to the operating state by performing a power-saving recovery operation on an operation unit and executes a copy job.
However, universal serial bus (USB) device control is often performed by using a USB device controller built in the high-performance main CPU. A common CPU is not provided with a function of separately controlling the power supply of the USB device controller and the power supply of other portions.
Therefore, if power supply to the main CPU stops in the sleep state, the built-in USB device controller also stops operation, thereby making it impossible to respond to a packet transmitted from a USB host. In the power-saving state, therefore, a print job cannot be executed via a USB device.
Although a method for continuing power supply to the main CPU in the power-saving state is effective, the main CPU provides high power consumption to control devices in addition to the USB device, which remarkably reduces the effect of the power saving measures. To cope with this problem, Japanese Patent Application Laid-Open No. 2009-187396 discusses a technique for supplying in the power-saving state the power to a USB device controller from a host apparatus such as a PC.
However, the technique discussed in Japanese Patent Application Laid-Open No. 2009-187396 supplies the power to the USB device controller from the host apparatus such as a PC, and, therefore, has a problem that the effect of the power-saving measures is not sufficient in the entire configuration including the PC although the power consumption of an MFP is reduced.